Zuke Maguro, with its mildly savory flavor and rich, slightly sticky texture, is an essential dish when exploring Japan’s tuna culinary culture. You can enjoy it on its own or as a topping for sushi or donburi (rice bowls).
Add sake and mirin to a pot and heat it over medium heat. Once it starts to boil, let it simmer for about 20 seconds to cook off the alcohol, then turn off the heat.
Add soy sauce to the pot and heat it again over low heat. Once small bubbles start to appear on the surface, turn off the heat immediately to preserve the soy sauce's flavor. Add kombu to the pot and let it cool to room temperature. The nikiri soy sauce for marinating is now ready.
Prepare ice water in a bowl.
Fill another pot with water and bring it to a boil. Once boiling, place tuna block on a ladle and gently submerge it into the hot water. Blanch it for about 10 seconds until the surface turns white, then remove it.
Place the tuna in the bowl of ice water to prevent the residual heat from overcooking the inside.
Remove the tuna from the bowl and gently pat it dry with paper towels. Place the tuna in a container and pour the cooled nikiri soy sauce over it. Cover the container tightly with plastic wrap or a well-sealed lid, and let it sit in the refrigerator for 3 to 8 hours, turning the tuna over halfway through to ensure even marination.
Cut the tuna into slices about ⅓ inch (9 mm) thick, or to your preferred thickness, and arrange them on a plate. Garnish with shiso leaves and wasabi, if desired. Alternatively, you can serve this dish as a topping for sushi or donburi (rice bowls).